Industrial processes often create and use a significant amount of thermal energy to heat various processes and also use significant amounts of water for many varied processes. Common byproducts of these industrial processes are, among other things, significant amounts of exhaust heat and contaminated liquids and/or contaminated water, or simply wastewater. The exhaust heat is commonly exhausted to the surrounding atmosphere, which frequently results in a significant waste in thermal energy. Wasting such thermal energy is both monetarily a net loss from the industrial process and usually increases the so-called “carbon footprint” or energy usage profile of the industrial process.
Further, the wastewater usually needs to be treated at some point, either at the site of the industrial process or at a location remote from the industrial process, to remove the contaminants from the water and/or other liquids. To treat wastewater, for example, it is common to separate the water from the contaminants to meet various purity targets or to reduce the volume of liquid water within a reservoir of wastewater. Such contaminants may include, for example, salts, sulfur, heavy metals, suspended soils, human or animal waste, oils, fertilizers, pharmaceuticals, acid and any other undesirable matter as would be apparent to a person of skill in the art. This treatment of the wastewater takes additional energy, further adding to the energy usage profile of the industrial process.
Outdoor open liquid reservoirs, such as retention ponds, aeration reservoirs, dry ponds, open-topped tanks, and the like, are often used to temporarily store wastewater that contains undesirable levels of contaminants until the wastewater can be treated to separate the contaminant from the water. After separation, the cleaned water can be released to the environment or otherwise used as desired, and the contaminants and/or concentrated wastewater can be further processed, recycled, transported to an appropriate landfill, and/or otherwise disposed of.
One commonly used method of at least initially separating non-volatile contaminants from the water is to evaporate the water from the wastewater, thereby releasing relatively clean water into the atmosphere in the gaseous state in the form of water vapor while the contaminants are retained and/or re-captured in the reservoir. Depending on the circulation of wastewater into the reservoir, after some period of time the water is either completely evaporated, thereby leaving the contaminants remaining in the reservoir for easy collection and disposal, or the concentration of contaminants is elevated to a point, which may exceed saturation in terms of the solubility of one or more contaminants, where it becomes economically advantageous to further process and/or separate the highly concentrated wastewater in other ways.
Although the water evaporates naturally at the surface of a pond or other open reservoir, it is often desirable to increase the rate of evaporation to decrease the processing time of the wastewater in order to increase economic efficiencies. Thus, it is common to place a reservoir evaporator system directly in the reservoir that effectively accelerates evaporation of the water to the surrounding environment by, for example, increasing the surface area to volume ratio of the wastewater to the surrounding air. There are many ways to accomplish this, and of course, the efficacy of this evaporative treatment method is highly dependent on many variables other than the evaporator system, including flow rate of wastewater into or through the reservoir, humidity levels of the surrounding environment, the liquid to be evaporated, and temperature, to name a few.
One known type of reservoir evaporator system uses nozzles to spray a fine mist of droplets of the wastewater up into the air above the top surface of the reservoir. Under ideal conditions, the water in the droplets evaporates into the surrounding atmosphere more quickly than from the top surface because of the increased surface area to volume ratio, and the contaminants and any un-evaporated droplets fall back into the reservoir. An exemplary reservoir evaporation system generally incorporating this design is disclosed in U.S. Patent Application Publication No. 2010/0139871 to Rasmussen et al.
Another known type of reservoir evaporator system floats on the top surface of the reservoir and includes a spinning agitator for scooping wastewater from the top surface and sprinkling it into the air. The agitator is connected to a source of high pressure air that spins the agitator by means of thrust nozzles, and the exhaust from the thrust nozzles may be directed to further impact the wastewater sprinkled into the air to further accelerate evaporation. An exemplary reservoir evaporation generally incorporating this design is disclosed in U.S. Pat. No. 4,001,077 to Kemper.
A further known type of reservoir evaporator system that dispenses with the use of high pressure air exposes evaporation surfaces that have been wetted with the wastewater to the air and wind. One exemplary reservoir evaporation system generally incorporating this design is disclosed in U.S. Pat. No. 7,166,188 to Kadem et al.
Although these known systems do accelerate the evaporation and therefore separation of water from a reservoir of wastewater, among other significant limitations, they frequently use a large amount of energy to do so.